Added test that demonstrates ability to set shader uniforms from python

Rendering/OpenGL2/Testing/Python/CMakeLists.txt

+set (RenderingOpenGL2PythonTests
+  TestUserShader2.py
+  )
+
+if ("${VTK_RENDERING_BACKEND}" STREQUAL "OpenGL2")
+  vtk_add_test_python(
+    ${RenderingOpenGL2PythonTests}
+    )
+endif ()

Rendering/OpenGL2/Testing/Python/TestUserShader2.py

+#!/usr/bin/env python
+'''
+=========================================================================
+
+  Program:   Visualization Toolkit
+  Module:    TestUserShader2.py
+
+  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
+  All rights reserved.
+  See Copyright.txt or http:#www.kitware.com/Copyright.htm for details.
+
+     This software is distributed WITHOUT ANY WARRANTY without even
+     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+     PURPOSE.  See the above copyright notice for more information.
+
+=========================================================================
+'''
+
+import sys
+import vtk
+from vtk.util.misc import vtkGetDataRoot
+
+'''
+  Prevent .pyc files from being created.
+  Stops the vtk source being polluted
+  by .pyc files.
+'''
+sys.dont_write_bytecode = True
+
+
+@vtk.calldata_type(vtk.VTK_OBJECT)
+def vtkShaderCallback(caller, event, calldata):
+    program = calldata
+    if program is not None:
+        diffuseColor = [0.4, 0.7, 0.6]
+        program.SetUniform3f("diffuseColorUniform", diffuseColor)
+
+
+renWin = vtk.vtkRenderWindow()
+renWin.SetSize(400, 400)
+iren = vtk.vtkRenderWindowInteractor()
+iren.SetRenderWindow(renWin)
+ren = vtk.vtkRenderer()
+ren.SetBackground(0.0, 0.0, 0.0)
+ren.GradientBackgroundOn()
+renWin.AddRenderer(ren)
+actor = vtk.vtkActor()
+ren.AddActor(actor)
+reader = vtk.vtkPLYReader()
+reader.SetFileName("" + str(vtkGetDataRoot()) + "/Data/dragon.ply")
+norms = vtk.vtkTriangleMeshPointNormals()
+norms.SetInputConnection(reader.GetOutputPort())
+mapper = vtk.vtkOpenGLPolyDataMapper()
+mapper.SetInputConnection(norms.GetOutputPort())
+actor.SetMapper(mapper)
+actor.GetProperty().SetAmbientColor(0.2, 0.2, 1.0)
+actor.GetProperty().SetDiffuseColor(1.0, 0.65, 0.7)
+actor.GetProperty().SetSpecularColor(1.0, 1.0, 1.0)
+actor.GetProperty().SetSpecular(0.5)
+actor.GetProperty().SetDiffuse(0.7)
+actor.GetProperty().SetAmbient(0.5)
+actor.GetProperty().SetSpecularPower(20.0)
+actor.GetProperty().SetOpacity(1.0)
+
+mapper.SetVertexShaderCode(
+    "//VTK::System::Dec\n"
+    "attribute vec4 vertexMC;\n"
+    "//VTK::Normal::Dec\n"
+    "uniform mat4 MCDCMatrix;\n"
+    "void main () {\n"
+    "  normalVCVSOutput = normalMatrix * normalMC;\n"
+    "  vec4 tmpPos = MCDCMatrix * vertexMC;\n"
+    "  gl_Position = tmpPos*vec4(0.2+0.8*abs(tmpPos.x),0.2+0.8*abs(tmpPos.y),1.0,1.0);\n"
+    "}\n"
+)
+mapper.SetFragmentShaderCode(
+    "//VTK::System::Dec\n"
+    "//VTK::Output::Dec\n"
+    "varying vec3 normalVCVSOutput;\n"
+    "uniform vec3 diffuseColorUniform;\n"
+    "void main () {\n"
+    "  float df = max(0.0, normalVCVSOutput.z);\n"
+    "  float sf = pow(df, 20.0);\n"
+    "  vec3 diffuse = df * diffuseColorUniform;\n"
+    "  vec3 specular = sf * vec3(0.4,0.4,0.4);\n"
+    "  gl_FragData[0] = vec4(0.3*abs(normalVCVSOutput) + 0.7*diffuse + specular, 1.0);\n"
+    "}\n"
+)
+
+mapper.AddObserver(vtk.vtkCommand.UpdateShaderEvent, vtkShaderCallback)
+
+renWin.Render()
+ren.GetActiveCamera().SetPosition(-0.2, 0.4, 1)
+ren.GetActiveCamera().SetFocalPoint(0, 0, 0)
+ren.GetActiveCamera().SetViewUp(0, 1, 0)
+ren.ResetCamera()
+ren.GetActiveCamera().Zoom(2.0)
+renWin.Render()
+iren.Start()